Source/JavaScriptCore/dfg/DFGDesiredWeakReferences.cpp

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#include "config.h"
#include "DFGDesiredWeakReferences.h"

#if ENABLE(DFG_JIT)

#include "CodeBlock.h"
#include "DFGCommonData.h"
#include "JSCJSValueInlines.h"

namespace JSC { namespace DFG {

DesiredWeakReferences::DesiredWeakReferences()
    : m_codeBlock(nullptr)
{
}

DesiredWeakReferences::DesiredWeakReferences(CodeBlock* codeBlock)
    : m_codeBlock(codeBlock)
{
}

DesiredWeakReferences::~DesiredWeakReferences()
{
}

void DesiredWeakReferences::addLazily(JSCell* cell)
{
    if (cell)
        m_references.add(cell);
}

void DesiredWeakReferences::addLazily(JSValue value)
{
    if (value.isCell())
        addLazily(value.asCell());
}

bool DesiredWeakReferences::contains(JSCell* cell)
{
    return m_references.contains(cell);
}

void DesiredWeakReferences::reallyAdd(VM& vm, CommonData* common)
{
    // We do not emit WriteBarrier here since (1) GC is deferred and (2) we emit write-barrier on CodeBlock when finishing DFG::Plan::reallyAdd.
    ASSERT(vm.heap.isDeferred());

    Vector<StructureID> weakStructureReferences;
    Vector<WriteBarrier<JSCell>> weakReferences;
    for (JSCell* target : m_references) {
        if (Structure* structure = jsDynamicCast<Structure*>(target))
            weakStructureReferences.append(structure->id());
        else {
            // There are weird relationships in how optimized CodeBlocks
            // point to other CodeBlocks. We don't want to have them be
            // part of the weak pointer set. For example, an optimized CodeBlock
            // having a weak pointer to itself will cause it to get collected.
            RELEASE_ASSERT(!jsDynamicCast<CodeBlock*>(target));
            weakReferences.append(WriteBarrier<JSCell>(vm, m_codeBlock, target));
        }
    }
    if (!weakStructureReferences.isEmpty() || !weakReferences.isEmpty()) {
        ConcurrentJSLocker locker(m_codeBlock->m_lock);
        ASSERT(common->m_weakStructureReferences.isEmpty());
        ASSERT(common->m_weakReferences.isEmpty());
        common->m_weakStructureReferences = WTFMove(weakStructureReferences);
        common->m_weakReferences = WTFMove(weakReferences);
    }
}

template<typename Visitor>
void DesiredWeakReferences::visitChildren(Visitor& visitor)
{
    for (JSCell* target : m_references)
        visitor.appendUnbarriered(target);
}

template void DesiredWeakReferences::visitChildren(AbstractSlotVisitor&);
template void DesiredWeakReferences::visitChildren(SlotVisitor&);

} } // namespace JSC::DFG

#endif // ENABLE(DFG_JIT)